1. Field of the Invention
The present invention relates generally to a structure of gears and bearings and, more particularly, to a particular structure relating to a bevel gear and a bearing adaptor which facilitates the manual assembly of the bevel gear and related thrust and roller bearings into a gearcase in combination with a bearing carrier assembly.
2. Description of the Prior Art
Those skilled in the art of marine propulsion systems are familiar with various types of gear and bearing structures contained within the gearcase of a marine propulsion system. Certain marine propulsion systems are provided with a gearcase internal assembly that is particularly configured to suit an opposite rotation of the propeller shaft. As an example, when two outboard motors are provided for use in a tandem operation on a single marine vessel, the gearing associated with the propeller shafts are selected and constructed to rotate in opposite directions. This technique is well known to those skilled in the art of marine propulsion systems. Because of the thrust forces resulting from the opposite rotation of the propeller and its shaft, the bearing arrangement in an opposite rotation marine propulsion system is designed differently than in a marine propulsion system with a conventionally rotating propeller shaft. These reverse rotating marine propulsion systems are sometimes referred to as “left hand” systems.
In a gearcase for an oppositely rotating propeller shaft, the bearing carrier assembly is provided with a clearance fit between the gear hub and the roller bearings. During assembly of the components into the gearcase, the bevel gear can slide out of the bearing carrier assembly because of this clearance fit and because the subassemblies are typically assembled in a direction with the axis of rotation of the bevel gears being vertical. This vertical assembly technique typically places the forward gear on the bottom of the subassembly with the bearing carrier above it. As a result of gravity and the clearance fit between the gear hub and the rollers, the bevel gear can easily separate from the bearing carrier during the assembly procedure. As a result, the assembly of the components into a gearcase for an opposite rotation marine propulsion system can be extremely difficult. Assembling the bevel gear into the other components of the bearing carrier requires precise alignment with numerous loose bearings, thrust rings, and O-rings being retained in a precise location as the components are fitted together. This difficult assembly and alignment of components increases the time necessary to assemble the marine propulsion system and, as a result, increases its cost and the likelihood that the components can be misassembled.
Various types of gearcase mechanisms and assemblies are known to those skilled in the art of marine propulsion systems.
U.S. Pat. No. 4,986,775, which issued to Wantz on Jan. 22, 1991, discloses a propeller shaft bidirectional thrust bearing system. The system for the propeller shaft of a marine propulsion system includes a substantially circumferential groove milled into the propeller shaft. A pair of substantially semicircular force transferring members are adapted for placement within the groove and front and rear bearing collars are placed adjacent the force transferring members. Front and rear needle bearings are provided adjacent the front and rear bearing collars, respectively. A front bearing adaptor, interconnected with the walls of the cavity within which the propeller shaft is disposed, transfers forward thrust to the propeller shaft in the gearcase. A rear bearing carrier, held in position by means of a ring nut mounted within the cavity, serves to transfer rearward thrust in the propeller shaft to the gearcase.
U.S. Pat. No. 4,897,058 which issued to McCormick on Jan. 30, 1990, discloses a marine device with an improved propeller shaft bearing carrier arrangement. A marine drive for a boat includes a construction wherein a propeller supporting bearing sleeve is disposed in a recess inside the propeller hub. A bearing carrier is concentrically associated with a propeller shaft. The carrier is provided with a rearwardly extending nose portion which is telescoped within the forwardly facing recess in an adjacent rearward propeller hub. The propeller shaft is journaled in the bearing device which is disposed between the carrier and the shaft and within the recess. In one aspect of the invention, the carrier is prevented from rotating about the shaft access. In another aspect, a sealing device is disposed between the propeller shaft and the rear end portion of an adjacent supporting gearcase. In the embodiment disclosed in this patent, dual propellers and dual bearing carriers are utilized, with bearing carrier noses disposed in recesses in both propeller hubs.
U.S. Pat. No. 4,373,922, which issued to Weed on Feb. 15, 1983, discloses an outboard propulsion gearcase. An outboard drive unit for a watercraft with a through-the-propeller hub exhaust system for engine exhaust has a bearing support member which carries the propeller shaft and separates the exhaust passages from the propeller shaft gears. Lubricant retaining surfaces are formed on the bearing support member to prevent corrosion between the support member and the housing.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Although some of the specific components and structures within the gearcase of a marine propulsion system can vary from one design to another, the basic structure incorporates the same types of components. The patents described above, illustrate three examples of a gearcase structure. For example, U.S. Pat. No. 4,986,775 shows the arrangement of a bearing carrier in conjunction with thrust bearings and bevel gears for the purpose of providing a transmission for the marine propulsion system. Two bevel gears are usually provided, in opposing directions, which are continuously engaged with a bevel gear that is attached to a driveshaft. By selectively engaging either a forward or reverse bevel gear into driving relation with the propeller shaft, forward or reverse direction can be selected by the operator of a marine vessel. Thus, with a constant direction of rotation of the driveshaft, the selection of the forward or reverse bevel gears will cause the rotation of the propeller shaft to change in accordance with the position of a dog clutch that is movable by the operator of the marine vessel. When neither of the two bevel gears is engaged with the propeller shaft, the transmission is placed in a neutral gear position.
The basic structure of the gears and bearings within a gearcase are generally known to those skilled in the art and will not be described in significant detail below other than is necessary to describe the present invention. The structure of the internal components of a gearcase for a marine propulsion system can be significantly improved if the configuration of the components can be made to facilitate the assembly of the components into a gearcase housing, particularly in conjunction with an oppositely rotating propeller shaft.